The present invention relates to an analytical apparatus and process, and more particularly to an apparatus and process for extracting pollutants from a waste water sample under pressure as a necessary step to analyzing the concentrations of such pollutants in the waste water sample.
Liquid-liquid contacting systems for use in solvent extraction operations are widely used. A principal object in the use of such systems is the contacting of immiscible or only partially miscible liquids to cause the transfer of dissolved substances from one liquid to another. Some such examples of prior art extraction systems are disclosed in U.S. Pat. Nos. 2,249,746; 3,260,572; 2,729,549; 3,403,980, 2,689,874; 3,226,092; 3,212,854 and 3,247,104.
In the area of monitoring and sampling water and waste water streams for pollutants, solvent extraction techniques have found use in extracting organic chemical compounds from the aqueous streams. The U.S. Environmental Protection Agency has issued regulations pursuant to section 304(h) of the Clean Water Act, 33 U.S.D. 1251 et. seq., which requires the agency to promulgate guidelines establishing test procedures for the analysis of pollutants. See generally 40 C.F.R. 136.
Although the ultimate analysis of many organic pollutants is performed using gas or liquid chromatography and mass spectrometry techniques, in many instances the organic pollutants are initially extracted from the water samples using solvent extraction. This is true for the analysis of pesticides and polynuclear aromatic hydrocarbon compounds as well as base/neutral and acid compounds.
At present, the two USEPA approved extraction methods are solvent extractions with vigorous manual shaking in a separatory funnel and a extraction technique in which a solvent having a higher specific gravity than water is passed through a continuous column of water containing the pollutant to be extracted and repeatedly recycled for an extended time period. However, each technique has significant disadvantages. The manual technique sometimes results in emulsions which are difficult and/or time consuming to break, requires the time and attention of a trained technician, and yields variable recoveries of extracted compounds. The continuous extraction technique, while being less subject to the formation of emulsions and requiring only relatively unattended operation, requires 24 to 48 hours to achieve one extraction, requires apparatus which is difficult to clean because of its complicated design and subject to breakage, and requires significant amounts of electrical power and cooling water to operate.
Accordingly, there exists a need in the art for an extracting and analyzing procedure which is relatively rapid, simple to use, and avoids the problems of prior art techniques.